A jet is now about as fuel-efficient as a car, when you look at payload delivered. Jets fly fully loaded. A car drives almost empty.

Now here's an industry that doesn't need direction from Congress on saving fuel: airlines. American Airlines and United know what fuel costs them--a lot. Jet engines are whirling, shrieking proof of how technology advances to burn more fuel, faster, in less space. So year after year the airlines hammer on the door of General Electric, demanding ever more efficient jet engines. Congress doesn't have to tell them to do this. They think of it all on their own.

And by golly, GE
(nyse:
GE -
news
-
people
) delivers. Per gallon consumed, you can go at least 100 times as far as Wilbur or Orville went at Kitty Hawk. Jet-engine efficiencies have risen sharply in the last 30 years. The airlines have used clever software to boost their effective efficiency even more. Has anyone else noticed that planes seem rather crowded these days? The airlines have learned to jigger prices to the point where they fill almost every seat.

Between GE and the seat-packing conspiracy, passenger miles per gallon have gone up and up. Astonishingly, a jet is now about as fuel-efficient as a car, when you look at payload delivered and recognize that jets fly fully loaded, while cars drive almost empty.

The one disappointing fact is that total consumption of civilian aviation fuel has gone up and up, too. How come? The Efficiency Paradox bites again. More efficient jet engines ... cheaper tickets ... more passengers ... more jets in the air.

The efficiency of combustion engines has been rising fast since James Watt launched the industrial age 250 years ago. The best external combustion engines were about 20% efficient at the beginning of the 20th century. By midcentury they were hitting 40%. Today's best exceed 50%. The internal combustion engines used in cars and trucks have been on roughly the same trajectory, but got started over a century after the steam engines did.

Collectively, combustion engines burn about 80% of all the thermal energy we use in the U.S. But the total amount of fuel they burn has risen right alongside their efficiency. The U.S. today consumes 100 quadrillion Btu (quads) of thermal energy a year. In 1950 the figure was 35 quads; in 1910, about 7 quads, not counting horse feed and other agricultural sources.

The efficiency of energy-consuming technologies always rises, with or without new laws from Congress. Total consumption of primary fuels rises alongside. The historical facts are beyond dispute: When jet turbines, steam power plants and car engines were much less efficient than they are today, they consumed much less total energy, too.

All smart politicians back "more efficiency" because that seems to let them embrace lower energy prices and less consumption as well. But to reduce energy consumption, we should probably mandate less efficiency, not more. Efficiency rises. Energy consumption rises, too. This is the great paradox of the efficiency. Read it and weep.

Peter Huber, a Manhattan Institute senior fellow, is the author of Hard Green: Saving the Environment from the Environmentalists and the Digital Power Report. Find past columns atwww.forbes.com/huber.

Stock quotes are delayed at least 15 minutes for Nasdaq, at least 20 minutes for NYSE/AMEX.
U.S. indexes are delayed at least 15 minutes with the exception of Nasdaq, Dow Jones Industrial Average and S&P 500 which are 2 minutes delayed.